رضا آذین

Sequestration of carbon dioxide in saline aquifers has become a renowned procedure owing to the availability of this type of reservoirs. Nevertheless, there is a possibility of a sudden leakage of CO2, mainly because this sequestration technique causes a long term interaction among CO2, rock and pore fluid, leading to an unexpected rise in permeability of the reservoir. Therefore, a systematic study is required in order for further evaluation of these interaction effects. Interactions of injected CO2, brine and rock during CO2 sequestration in saline aquifers change their natural hydro-mechanical properties, a?ecting the safety and efficiency of the sequestration process. Core level study storage mechanism of CO2 at laboratory scale have shown to be of a great help for CO2 geological storage studies. This study aims to identify these induced interactions’ changes in aquifer, and particularly their influence on the reservoir rock properties like porosity and permeability. The core samples of aquifer formations, collected from Iranian Asmari formations in Fars province, have significant quantities of dolomite revealed by XRD analysis. The objective of this work is to understand interaction of CO2-saturated brine carbonate under reservoir conditions. A series of core-flood experiments were carried out to assess the potential of dolomites to buffer brine and further promote mineral precipitation over time. Carbonate samples were exposed to CO2 for 2 weeks and 4 weeks. The dissolution and precipitation of minerals were investigated using CBCT to determine the impact of these processes on rock properties. The results showed that long term (4 weeks) reaction with CO2 causes salt precipitation in the core samples which is seen with the help of FE-SEM and EDX, plus changing pore structure and rock porosity. The ICP and IC analysis tests showed that long-term CO2 reaction also creates a significant CO2 drying-out e?ect and salt crystallization in the aquifer’s rock pore space